The invention relates to candle filter elements which are fixed in a hanging position to a collector tube inside a pressure vessel for the aseptic and/or sterile filtration of liquids, including a coupling with a conical upper coupling part, a conical lower coupling part, and a part of cams.
One candle filter element of this type which is suitable for sterile filtration in a pressure vessel is known from WO 94/23819. In order to clean the filter elements, one can remove the central tube serving as a support body without having to open the filter container. The couplings used can only be sterilized internally in place, and cannot be properly cleaned without dismantling.
Besides screw-type fasteners, quick-acting fasteners are also used for fixing candle filter elements. For instance, CH-A 660850 describes one such quick-acting fastener which is suitable for filtration of radioactive effluents and which enables the filter elements to be exchanged easily by means of a turn-lock fastener. However, such a fastener is not suitable for aseptic or sterile use.
The problem of the invention is to make available a device for connecting pressurized filter elements in a pressure vessel that is suitable for aseptic or sterile use.
In accordance with the invention this problem is solved by providing a rinse opening between the upper coupling part, the lower coupling part and the cams.
The essential advantage is that one coupling part is provided with rinse openings so that the cavities between the opposing internal surfaces of the two coupling parts can be rinsed with CIP liquid and/or sterilized with steam.
The coupling parts are connected in an advantageous manner by being turned relatively to each other so that fastening cams and opposing cams engage in each other and the sealing faces are pressed against each other by a rising pitch on the fastening cams or opposing cams.
As a connection for elements with a vertical axis, both coupling parts are made with a conical shape, to allow liquid to drain out of the interstices. Owing to the conical shape, the sealing faces are located close to the bore of the tube. They have the smallest possible cross-section which is provided for the connection required cross-section rinse openings and has no surfaces in direct contact with each other apart from the bearing points of the cams. The connection requires at least two pairs of cams, and preferably three.
As a coupling for filter elements, it is an advantage for the connecting cams to be located on a large diameter so that the lever arm to sustain forces acting radially on the filter elements is as large as possible. Either cam (upper or lower) may be the larger of the two.
The cam may be pressed axially by the lower coupling part and/or by the upper coupling part. The rising pitch must be selected so that axial pressure is brought to bear on the seal.
In a variant, the seal can be arranged so that it also seals radially, so that none of the cams need have a rising pitch.
It is convenient to provide a fixed dip tube, in other words a dip tube that is not freely rotatable.